1. Field of the Invention
The present invention relates to surgical or medical instruments of the forceps-type conventionally used for clamping and manipulating body tissues or organs and, more particularly, to a mechanism for selectively applying different locking forces on the jaws of such an instrument.
2. Background Art
Conventional forceps-type instruments normally include a pair of pivoted forceps jaws which function in a scissors-like action and are used in medical operations or surgery to hold, expose and manipulate tissues. The jaws may be self-biased to an open condition at the distal end of the instrument to define a V-shaped receptacle. A pair of graspable and relatively movable handles at the proximal end of the instrument are squeezed together to close the open distal jaw ends so as to grasp tissues, needles or the like between the jaws.
With the conventional forceps-type clamping instruments described above, activation of the jaws is accomplished by scissors-type action between the handles, requiring cumbersome manual manipulation by a surgeon and, over a prolonged use, may cause fatigue and tremors due to the necessary unnatural movements of the intrinsic hand muscles. Once the jaws are moved to a pressure-applying position, the unwieldy handle arrangement restricts the precision and finesse with which the instrument may be operated.
Activation of the jaws of conventional forceps-type instruments is limited to a single plane, i.e., the plane including the forceps jaws. Because the plane including the forceps jaws is generally coincident with the plane in which the handles move, the surgeon's hand frequently must be uncomfortably rotated to a position which accommodates the necessary displacements of the handles. In order to properly position the instrument, it is necessary to rotate the entire hand at the surgeon's elbow or at the shoulder. Such movements are quite crude in comparison to movements created by the intrinsic hand muscles and limit the degree of precision with which the jaws may be controlled.
Another problem with conventional forceps-type instruments is that the desired force to be applied by the jaws to an object must be manually maintained. This may further add to the discomfort during use as the surgeon squeezes the handle and simultaneously rotates the hand. Inevitably, the force exerted by the jaws varies as the hand is repositioned. This may result in the needle or other object held by the jaw slipping within the jaws or altogether falling out.
The prior art instruments are either in normally closed or open positions. For those in a normally closed position, a substantial amount of force must be exerted by the user to effect opening of the jaws. Since it is common to repeatedly open and close the jaws to effect a desired grip, as during a suturing operation, it is not uncommon for the user of such instruments to suffer hand fatigue. Those instruments that are normally open require a substantial amount of closing force which similarly fatigues the user's hand upon repeated manipulation of the jaws.
A still further problem with the prior art instruments is that the amount of pressure exerted by the jaws on an object cannot be readily consistently applied. Instead, the user roughly gauges the jaw pressure by the amount of pressure applied through the handles.